Move package/subpackage version inside package source

[aaraney]

This PR moves package versions' from setup.cfg to src/<subpackage>/_version.py in an attribute named __version__. An attr: directive is used in setup.cfg to access this versioning information for packaging metadata purposes.

Ive tested installing subpackages locally in editable and non-editable modes. Likewise, Ive also tested that both wheels and tar gz archives of a subpackage created using python -m build also install properly without issue. That is not to say there is not a way to break it though.

Note: it is required that the __version__ attribute be imported in a subpackage's top level __init__.py. See setuptools #1753 for more detail. I don't think this is a deal breaker (meaning adding complexity to the packaging process) and overly boiler plate, given that in the future I would like to introduce a public api for each subpackage that discriminates the current subpackage version to the user.

Changes

• Subpackage version's are now held in an attribute __version__ in a _version.py file. (this file sits even with the top level __init__.py).

Todos

• Determine if changes to events are required after the discussion in Events package structure question #141 .

Checklist

• PR has an informative and human-readable title
• PR is well outlined and documented. See #12 for an example
• Changes are limited to a single goal (no scope creep)
• Code can be automatically merged (no conflicts)
• Code follows project standards (see CONTRIBUTING.md)
• Passes all existing automated tests
• Any change in functionality is tested
• New functions are documented (with a description, list of inputs, and expected output) using numpy docstring formatting
• Placeholder code is flagged / future todos are captured in comments
• Reviewers requested with the Reviewers tool ➡️

[jarq6c]

Looks good. I checked all the versions locally.